Patent application title: BLOCK MOUNTED LOCK-OUT MECHANISM

Abstract:

A differential is provided that includes a first and second side gear and
a reaction block disposed between the first and second side gear. The
differential further includes an engagement mechanism configured to have
at least a portion of the engagement mechanism that is moveable from a
retracted position to an extended position and a lock-out mechanism that
is configured to engage the portion of the engagement mechanism. The
lock-out mechanism is mounted to the reaction block. A reaction block for
a differential in which a lock-out mechanism is mounted on the reaction
block is also provided.

Claims:

1. A differential comprising:a first and second side gear;a reaction block
disposed between the first and second side gear;an engagement mechanism
configured to have at least a portion of the engagement mechanism
moveable from a retracted position to an extended position; anda lock-out
mechanism configured to engage and at least partially control the
movement of the engagement mechanism,wherein the lock-out mechanism is
mounted to the reaction block.

2. The differential of claim 1, wherein the engagement mechanism comprises
a differential governor, and the lock-out mechanism comprises a latching
bracket.

3. The differential of claim 1, further comprising a lockup means for the
differential, the lockup means comprising a clutch pack and a clutch cam
plate, wherein the lockup means is actuated by the engagement mechanism
and lock-out mechanism.

4. The differential of claim 3, wherein the clutch cam plate defines a set
of external teeth on a radially outward surface and defines a cam surface
with a plurality of cam ramps.

5. The differential of claim 4, wherein the side gear defines a cam
surface with a plurality of cam ramps and a plurality of detents that
correspond to the plurality of cam ramps on the clutch cam plate.

6. The differential of claim 1, wherein the portion of the engagement
mechanism moveable from a retracted position to an extended position
comprises at least one flyweight.

7. The differential of claim 6, wherein the at least one flyweight is
rotatable about an axis that is oriented generally parallel to the axis
of rotation of the first and second side gear.

8. The differential of claim 7, wherein the at least one flyweight defines
a stop surface that is moveable from a retracted position to an extended
position in response to a predetermined extent of a differentiating
action.

9. The differential of claim 8, wherein the lock-out mechanism includes a
pawl.

10. The differential of claim 9, wherein the stop surface of the flyweight
is configured for engagement with the pawl of the lock-out mechanism when
the stop surface is in an extended position.

11. The differential of claim 1, wherein the reaction block is configured
to transfer force between the first and second side gears.

12. A differential comprising:a case;at least one pinion gear disposed in
the case;a first and second side gear disposed in the case and in meshed
engagement with the at least one pinion gear;a lockup means operable to
retard differential action of the differential;an actuating means for
actuating the lockup means; anda reaction block disposed in the case
between the first and second side gears,wherein the actuating means
comprises an engagement mechanism rotatable about an axis oriented
generally parallel to the axis of rotation of the first and second side
gear, the engagement mechanism including at least one flyweight, and
wherein the actuating means further comprises a lock-out mechanism
configured to engage the at least one flyweight of the engagement
mechanism when the at least one flyweight is in an extended position,
andwherein the lock-out mechanism is mounted on the reaction block.

13. The differential of claim 2, further comprising an input gear
connected to the case.

14. The differential of claim 2, wherein the first and second side gears
are in splined engagement with a pair of axle shafts.

15. A reaction block for a differential comprising:an engagement mechanism
comprising at least one flyweight member configured to extend outwardly
when a predetermined amount of differentiating action is provided; anda
lock-out mechanism comprising a pawl configured to receive the at least
one flyweight member and at least partially control movement of the
engagement mechanism,wherein the lock-out mechanism is mounted on the
reaction block.

16. The reaction block of claim 15, wherein the engagement mechanism
includes an arm configured for connecting the engagement mechanism to the
lock-out mechanism.

17. The reaction block of claim 15, wherein the lock-out mechanism
includes a shaft and the reaction block includes at least one projection
having at least one aperture for receiving the shaft of the lock-out
mechanism.

18. The reaction block of claim 15, wherein the reaction block includes a
plurality of projections configured to support the lock-out mechanism.

19. The reaction block of claim 18, wherein each of the plurality of
projections are substantially parallel to each other.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a block mounted lock-out mechanism,
including a block mounted lock-out mechanism for a differential.

BACKGROUND

[0002]One type of differential gear mechanism may commonly be referred to
as a "locking differential." In particular, one type of locking
differential may be referred to as a "mechanical locker" (i.e., a locking
differential in which the locking function occurs in response to the
operation of a mechanical device, as opposed to hydraulic actuation or
electromagnetic actuation). A conventional locking differential may
utilize a lockout mechanism (e.g., flyweight mechanism) to initiate the
lock-up of the differential clutch, wherein the lock-out mechanism is
configured to retard rotation of the cam plate relative to the
differential input (e.g., the ring gear and the differential case).
Locking differentials that utilize a lock-out mechanism to initiate
clutch engagement may be made in accordance with the teachings of any one
or more of U.S. Pat. Nos. 3,606,803; 5,484,347, and 6,319,166, all of
which are assigned to the assignee of the present invention and
incorporated herein by reference. Although these patents have been
incorporated by reference, the present invention is not limited to only
those locking differentials that are made in accordance with the
teachings of the referenced patents.

[0003]Conventionally, the lock-out mechanism may be mounted on the
differential case. While case-mounted lock-out mechanisms have been in
widespread commercial usage and provide sufficient performance
characteristics, it may be desirable to avoid mounting the lock-out
mechanism on the differential case. For example, the conventional
case-mounting of the lock-out mechanism requires a bushing and associated
drilling operation that increases complexity and cost of production.
Second, increased capitalization is required for machining and assembling
the differential case to be configured to receive the lock-out mechanism.

SUMMARY

[0004]A differential is provided that includes a first and second side
gear and a reaction block disposed between the first and second side
gear. The differential further includes an engagement mechanism
configured to have at least a portion of the engagement mechanism that is
moveable from a retracted position to an extended position and a lock-out
mechanism that is configured to engage the portion of the engagement
mechanism. The lock-out mechanism is mounted to the reaction block.

[0005]A reaction block for a differential is also provided that includes
an engagement mechanism and a lock-out mechanism, in which the lock-out
mechanism is mounted on the reaction block. The engagement mechanism
comprises at least one flyweight member configured to extend outwardly
when a predetermined amount of differentiating action is provided, and
the lock-out mechanism comprises a pawl configured to receive the at
least one flyweight member and at least partially control movement of the
engagement mechanism.

[0006]A differential with a block mounted lock-out mechanism (e.g., a
lockout mechanism mounted to the reaction block) in accordance with the
present invention may eliminate the conventional bushing and associated
drilling operation required for case-mounting of the lock-out mechanism
and may make machining and assembly of the differential case less complex
and costly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]Embodiments of the invention will now be described, by way of
example, with reference to the accompanying drawings, wherein:

[0008]FIG. 1 is an exploded view of a mechanical locking differential.

[0009]FIG. 2 is a perspective view of the mechanical locking differential
of FIG. 1.

[0010]FIG. 3 is a first cross-sectional view of a block mounted lock-out
mechanism in accordance with the present invention for use in a
mechanical locking differential.

[0011]FIG. 4 is a second cross-sectional view of a block mounted lock-out
mechanism in accordance with the present invention for use in a
mechanical locking differential.

DETAILED DESCRIPTION

[0012]Reference will now be made in detail to embodiments of the present
invention, examples of which are described herein and illustrated in the
accompanying drawings. While the invention will be described in
conjunction with embodiments, it will be understood that they are not
intended to limit the invention to these embodiments. On the contrary,
the invention is intended to cover alternatives, modifications and
equivalents, which may be included within the spirit and scope of the
invention as embodied by the appended claims.

[0013]FIG. 1 is an exploded view of a mechanical locking differential 10
that generally exhibits certain operations, features, and/or teachings
known to those of skill in the art. Differential 10 is configured to
allow two wheels on a motor vehicle to operate at different speeds and
maintain free differential action. However, if one wheel begins to slip,
the drive axle may be automatically and fully locked side to side,
thereby providing full power to both wheels. Differential 10 includes a
case 12. Case 12 may include a first end (e.g., flange end) 13 and a
second opposing end (e.g., bell end 15). Case 12 may be configured to
define a gear chamber and house various other components of differential
10. Torque input to differential 10 may be by means of an input gear
(e.g., ring gear) (not shown). The input gear may be attached to case 12
by any means conventional in the art, including, but not limited to a
plurality of bolts. The input gear (e.g., ring gear) may be in toothed
engagement with an input pinion gear (not shown), which receives input
drive torque from the vehicle driveline.

[0014]Differential 10 may further include a differential gear set disposed
within the gear chamber of case 12. In particular, differential 10 may
include two side gears 14, 16, thrust shims 18, 20, two pinion gears 22,
24, a pinion shaft (e.g., cross-shaft) 26, and a pinion shaft lock screw
28. The pinions gears 22, 24 may be rotatably mounted on the pinion shaft
26. The pinion shaft 26 may be connected to case 12 by any means
conventional in the art. The pinion gears 22, 24 may comprise the input
gears of the differential gear set disposed within the gear chamber of
case 12. The pinion gears 22, 24 may be in meshing engagement with side
gears 14, 16. The side gears 14, 16 comprise the output gears of the
differential gear set disposed within the gear chamber of case 12. The
side gears 14, 16 may be in splined engagement with a pair of axle shafts
(not shown) of a motor vehicle, for example. Case 12 may include annular
hub portions 29 on opposing ends of case 12 that are configured to
surround the axle shafts. Typically, bearing sets (not shown) are mounted
on the hub portions 29 to provide rotational support for the differential
gear mechanism.

[0015]During normal, straight-ahead operation of the vehicle, there may be
limited differentiating action (e.g., substantially no differentiating
action) that may occur between the left and right axle shafts, and the
pinion gears 22, 24 may not rotate relative to the pinion shaft 26.
Accordingly, the case 12, the pinion gears 22, 24, the side gears 14, 16,
and the axle shafts (not shown) all rotate about an axis of rotation (A)
of the axle shafts, as a solid unit. Under certain operating conditions,
such as when the vehicle is turning, a certain amount of differentiating
action may occur between the side gears 14, 16, up to a predetermined
level of speed difference. Above that predetermined level (e.g., above a
difference of about 100 RPM between the side gears 14, 16), it may be
desirable to retard the relative rotation between each of the side gears
14, 16 and the gear case 12, to prevent excessive differentiating action
between the axle shafts.

[0016]To retard differentiating action between the axle shafts, the
differential 10 may be provided with a lockup means for locking up the
differential gear set, and an actuating means for actuating the lockup
means. For example, the lockup means may comprise clutch packs 30, 32.
Clutch pack 30 may comprise a flange end clutch pack 30 and may be
located at the flange end 13 of case 12. Clutch pack 32 may comprise a
bell end clutch pack 32 and may be located at the bell end 15 of case 12.
As is known in the art, the clutch pack 30 may include a plurality of
inner clutch discs and a plurality of outer clutch discs. The inner
clutch discs may include radially outwardly extending "ears." The "ears"
may fit into guide holes in the differential case 12. Accordingly, the
inner clutch discs may turn with the case 12. The outer clutch discs may
include splines (e.g., include teeth on the inner radial surface of each
of the plurality of outer clutch discs). The splines on the outer clutch
discs may be configured for engagement with the external splines of the
side gears 14, 16. Accordingly, the outer clutch discs may turn with the
axle shafts and/or wheels.

[0017]The lockup means may further include a clutch cam plate 34 and a
wave spring 36. As is known is the art, the clutch cam plate 34 may be
configured to affect movement of the clutch pack 30 from a disengaged
condition to an engaged (e.g., "loaded") condition. In the engaged (e.g.,
"loaded") condition, the clutch pack 30 may be effective to retard
relative rotation between the case 12 and the side gear 14, thus
retarding and/or minimizing differentiating action between the side gears
14, 16. The clutch cam plate 34 may define a set of external teeth on a
radially outwardly extending outer surface. The clutch cam plate 34 may
also define a cam surface with a plurality of cam ramps. Side gear 14 may
also define a cam surface with a plurality of cam ramps and a plurality
of detents machined into the cam surface (e.g., the backside of the side
gear 14). The cam ramps on side gear 14 may correspond with the cam ramps
on clutch cam plate 34. The mating detents on the side gear 14 may
prevent the clutch cam plate 34 from ramping until a predetermined torque
is applied at the external teeth of the clutch cam plate 34. Accordingly,
during normal, straight-ahead operation of the vehicle (e.g., with little
or no differentiating action occurring), the cam surfaces of the side
gear 14 and the clutch cam plate 34 remain in a neutral position (i.e.,
no ramping) with the clutch cam plate 34 rotating with the side gear 14
at the same rotational speed. By retarding rotation of the cam clutch
plate 34 (e.g., by application of torque to the external teeth of the
clutch cam plate 34) relative to the side gear 14, movement of the clutch
pack 30 may be achieved because of the "ramping" of the cam surfaces of
the side gear 14 and the clutch cam plate 34. When the clutch cam plate
34 rotates out of the detents on side gear 14, the cam ramps on the
clutch cam plate 34 engage the cam ramps on the backside of side gear 14.
As the clutch cam plate 34 continues rotating, it moves axially toward
the side gear 14 and applies pressure to the clutch pack 30. Wave spring
36 is configured to apply pressure to the clutch cam plate 34 in order to
try to maintain the clutch cam plate 34 in the detent position (i.e., so
that the cam ramps on the clutch cam plate 34 and backside of side gear
14 are not engaged). The axial pressure from the axial movement of the
clutch cam plate 34 must, therefore, be sufficiently strong to move the
clutch cam plate 34 against the pressure applied by the wave spring 36.

[0018]An actuating means 38 for actuating the lockup means may be utilized
to retard rotation of the clutch cam plate 34 relative to the side gear
14. For example, the actuating means 38 may comprise an engagement
mechanism 40 and a lock-out mechanism 42. Referring now to FIG. 2
illustrating an assembled mechanical locking differential, the engagement
mechanism 40 may comprise a differential governor. The engagement
mechanism 40 may be mounted within the case 12 for rotation about its own
axis. The engagement mechanism 40 may include a plurality (e.g., two)
spring loaded flyweights 44. The flyweights 44 may comprise cylindrical
flyweights. The engagement mechanism 42 may further include an externally
geared portion 46, which is in engagement with the external teeth of the
clutch cam plate 34. The flyweights 44 may be rotatable about an axis
that is oriented generally parallel to the axis of rotation (A). The
flyweights 44 may each define a stop surface that is movable from a
retracted position to an extended position in response to a predetermined
extent of differentiating action. The flyweights 44 may also define a
pivot axis generally parallel to and spaced apart from the axis around
which the flyweights 44 are rotatable. The stop surfaces of the
flyweights 44 are generally oppositely disposed from the pivot axis.

[0019]The flyweights 44 may be coupled to the externally geared portion 46
via end caps 48, 50 that serve as spring-loaded cone clutches to cushion
their engagement with lock-out mechanism 42 (e.g., latching bracket). The
lock-out mechanism 42 of the actuating means 38 may comprise a latching
bracket. The lock-out mechanism 42 (e.g., latching bracket) may include a
pawl 52.

[0020]During operation, if the differentiating action begins to occur
between the axle shafts (e.g., there is a speed differential between the
two wheels), the side gear 14 and clutch cam plate 34 may begin to rotate
in unison at a speed different than that of the case 12, thereby causing
the engagement mechanism 40 to begin to rotate about its axis. As the
speed of the rotation of the engagement mechanism 40 increases,
centrifugal force may cause the flyweights 44 to move outward. When the
speed differential between the wheels is at or above about 100 RPM, there
may be enough centrifugal force on the flyweights 44 of the engagement
mechanism 40 to overcome a centering spring 54 and open (e.g., move out).
The flyweights 44 may move outward until one of the stop surfaces of the
flyweights 44 engages pawl 52 on the lock-out mechanism 42 (e.g.,
latching bracket), preventing further rotation of the engagement
mechanism 40. When the engagement mechanism 40 stops rotating, the
engagement of the geared portion 46 and the external teeth on the clutch
cam plate 34 causes the clutch cam plate 34 to rotate at the same speed
as the case 12 (which is different than the speeds of rotation of the
side gear 14), resulting in ramping, and initializing engagement of the
clutch pack 30. In other words, the stopped flyweight 44 may cause the
geared portion 46 to rotate the clutch cam plate 34 out of its detent
position, thereby triggering a ramping action and lock-up. When the
clutch cam plate 34 is ramped against the side gear 14, the ramping
increases until both axles turn at the same speed (e.g., full lock),
which may prevent further wheel slip. The differential 10 may unlock at
speeds below about 20 mph (e.g., 32 kph) when a slight torque reversal is
sensed at under 100 RPM differentiation (e.g., when the vehicle is going
straight and there is substantially equal traction side-to-side or there
is a slight turning (i.e., differentiating) in the direction opposite the
original lock).

[0021]The lock-out mechanism 42 (e.g., latching bracket) may have a safety
feature that is configured to allow it swing out of the reach of the
flyweights 44 of the engagement mechanism 40 at speeds above about 20 mph
(e.g., about 32 kph) in order to prevent lock-up from occurring. The
safety feature, therefore, allows lockup only at low vehicle speeds since
lock-up at higher speeds would have significant adverse effects on
steering. A locked differential has a tendency to drive a vehicle
straight and resist cornering.

[0022]Differential 10 may further include a reaction block or thrust block
56. Reaction block 56 may be configured to provide an axial link between
the clutch cam plate 34 as it ramps and begins to move axially toward the
opposing side gear 16, in order to apply clutching pressure to the clutch
pack 32 located at the bell end 15 of the differential case 12. Force
from a side gear 14 may be transferred through the reaction block 56 to
the other side gear 16, which transfers the force to the clutch pack 32.
Similarly, force from a side gear 16 may be transferred through the
reaction block 56 to the other side gear 14, which transfers the force to
the clutch pack 30. Accordingly, both side gears 14, 16 may be fully
locked to the differential case 12, which may lock both axle shafts and
their corresponding wheels and tires together to provide maximum
traction. The reaction block 56 may be disposed within case 12 and may
include one or more apertures to receive the pinion shaft 26.

[0023]The present invention may be substantially identical and
functionally equivalent to the locking differential described herein,
except that the actuating means 38 and reaction block 56 may be modified.
The actuating means 38 may be mounted to the reaction block 56. Referring
now to FIGS. 3-4, a block mounted lock-out mechanism 42 in accordance
with teachings of the present invention for use in a mechanical locking
differential is illustrated. Reaction block 56 may include one or more
projections 58, 60 at one end of reaction block 56. Each of the
projections 58, 60 may extend outwardly away from reaction block 56 in
the same direction (i.e., be substantially parallel to each other).
Referring to FIG. 4, the projections 58, 60 may be oppositely located
relative to each other and may include an opening 61 disposed
therebetween. Each of the projections 58, 60 may include an aperture 62
(illustrated in FIG. 3). Aperture 62 may be located toward the most
outward area of projections 58, 60. For example, projections 58, 60 may
have a generally or substantially triangular shape, and an aperture 62
may be located proximate the apex of the triangular shaped projections in
an embodiment of the invention. Referring again to FIG. 4, lock-out
mechanism 42 may include a shaft 64. Shaft 64 of lock-out mechanism 42
may be configured to be disposed in apertures 62 of projections 58, 60 of
reaction block 56. Lock-out mechanism 42 may include pawl 52. The
lock-out mechanism 42 may maintain a pivoting relationship with the
engagement mechanism 40. Referring now to FIG. 3, engagement mechanism 40
includes an arm 66 configured for connection and/or attachment to
lock-out mechanism 42. As described herein, engagement mechanism 40 may
be configured for rotation about its own axis and may include a plurality
of flyweights that are rotatable and each include a stop surface that is
moveable from a retracted position to an extended position for engagement
with pawl 52 on lock-out mechanism 42.

[0024]Lock-out mechanism 42 is combined (e.g., directly connected) with
the reaction block 56 so as to form a single sub-assembly, thereby
benefiting the overall assembly process. Lock-out mechanism 42 is not
directly connected to and/or mounted to the case 12. The combination of
the lock-out mechanism 42 with the reaction block may provide several
beneficial improvements. Among other things, the lock-out mechanism 42
mounted on the reaction block 56 can eliminate the necessity of a bushing
(e.g., a shaft to case bushing). In contrast, referring now to FIGS. 1-2,
bushing 68 is required between the shaft of the lock-out mechanism 42 and
the case 12 when the lock-out mechanism 42 is mounted on the case 12.
Further, the lock-out mechanism 42 mounted on the reaction block 56 in
accordance with the present invention can eliminate the corresponding
machined bushing hole 70 in the case 12, as well as other associated
assembly and machining labor and tooling. In contrast, referring again to
FIGS. 1-2, machined bushing hole 70 is otherwise required for mounting
the lock-out mechanism 42 on the case 12. Moreover, the lock-out
mechanism 42 in accordance with teachings of the present invention may
also eliminate machined holes in the case 12 for supporting the ends of
the engagement mechanism 40. In contrast, referring again to FIGS. 1-2,
machine holes 72 are otherwise required for mounting the engagement
mechanism 40 on the case. Additionally, the lock-out mechanism in
accordance with teachings of the present invention may be configured for
use with smaller differential applications in which space constraints may
be of greater concern.

[0025]The foregoing descriptions of specific embodiments of the present
invention have been presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed, and various modifications and
variations are possible in light of the above teaching. The embodiments
were chosen and described in order to explain the principles of the
invention and its practical application, to thereby enable others skilled
in the art to utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated. The
invention has been described in great detail in the foregoing
specification, and it is believed that various alterations and
modifications of the invention will become apparent to those skilled in
the art from a reading and understanding of the specification. It is
intended that all such alterations and modifications are included in the
invention, insofar as they come within the scope of the appended claims.
It is intended that the scope of the invention be defined by the claims
appended hereto and their equivalents.